SEA01FA089

During an instructional flight, radar data identified the helicopter maneuvering in level flight before making a rapid descent below radar coverage. About 33 seconds later, the helicopter was picked up on radar in a climbing right turn, then a left turn before radar contact was lost at an altitude of 1,500 feet MSL (1,060 AGL). Witnesses in the area reported observing the helicopter make "some radical flight maneuvers" before it lost altitude. The witnesses reported that the helicopter then descended in a "nose down" or "wobbling" attitude while it spun to the ground. Prior to ground impact, several witnesses observed an object or objects separating from the helicopter before they lost site of it in the trees. Two of the witnesses reported seeing the tail rotors separate followed by the tail section. The helicopter then collided with trees. During the on-site and post-accident investigation, it was determined that the tail rotor blades made contact with the side of the tail boom. The empennage assembly was found about 180 feet away from the main wreckage. Both tail rotor blades separated from the tail rotor hub. Components that separated were due to overload. Although a pitch change link and teeter bumper stop were not recovered, metallurgical examination of the tail rotor pitch control assembly determined that they were attached at impact. There was no evidence that pitch change control was lost prior to the tail rotor blade striking the tail boom. No evidence of a mechanical failure or malfunction was found. Further investigation determined that abrupt application of full left pedal during a simulated power failure could result in excessive flapping of the tail rotor and possible tail rotor blade contact with the tail boom. At the time of the accident, the mean tail rotor blade angle was 21.5 degrees to 22.0 degrees. Approximately three months after the accident, the manufacturer issued a service bulletin to re-rig the tail rotor to reduce maximum blade angle at the left pedal stop and required the installation of a harder teeter bumper. The mean tail rotor blade angle was changed to 16.5 degrees to 17.0 degrees.

History of flight

On May 11, 2001, approximately 0922 Pacific daylight time, a Robinson R44, N111PH, registered to a private individual and operated by Classic Helicopter Corp., as a 14 CFR Part 91 instructional flight, experienced an in-flight breakup while maneuvering about three miles south of Gorst, Washington. Visual meteorological conditions prevailed at the time and no flight plan was filed. The helicopter was destroyed by impact damage and post-crash fire. Both the flight instructor and private pilot were fatally injured. The flight originated from Boeing Field, Seattle, Washington, about 15 minutes prior to the accident.

Most witnesses were at various locations on the Trophy Lake Golf Course located about one-quarter to one-half mile away. One witness reported that he heard a sound and glanced up to see the helicopter initially traveling toward the golf course, then looked as if forward flight stopped before it made "some radical flight maneuvers." The witness described a sound difference with the main rotors before it lost 75 to 100 feet in altitude. The helicopter then made a "radical snap roll" maneuver before beginning a "cork-screw" dive. Prior to impact, the witness noticed that at about 200 to 250 feet above ground level, the tail rotors separated followed by the tail section separation at about 100 to 150 feet AGL. The witness then lost sight of the helicopter in the trees. Shortly thereafter, the witness heard an explosion and observed smoke. One other witness reported similar circumstances.

Several other witnesses reported hearing a "loud bang," "popping," "coughing," or "rough running" engine noise which brought their attention to the helicopter. Each of the witnesses reported observing the helicopter in a "nose down" or "wobbling" attitude while it spun, nose left, to ground impact. Prior to ground impact, the witnesses observed an object or objects separating from the helicopter.

Personnel information

Personnel at Classic Helicopter reported that the flight instructor was also the Director of Operations for Classic Helicopter. The instructor held flight certificates for commercial and flight instructor instrument operations, and rated in rotorcraft. The flight instructors total flight time in all helicopters was estimated as 11,200 hours, with 252 hours in the make and model helicopter involved in the accident. The instructor held a Class II medical certificate dated 1/31/01, with a limitation to wear corrective lenses. The week prior to the accident, the instructor flew 1.6 hours in a Bell 206, 1.3 hours in a Robinson R22, and 6 hours in another Robinson R44 operated by Classic Helicopter.

The second pilot, seated in the right seat, was receiving instruction and building flight time in preparation for the purchase of his own Robinson R44. At the time of the accident, the second pilot held a private pilot certificate for single-engine land aircraft and helicopter operations. The pilot's total flight time was estimated as 451 hours, with 386 hours in rotorcraft and 65 hours in fixed wing aircraft. The pilot had accumulated 6.5 hours of the company required 10 hours of dual flight time in the R44. The pilot held a Class III medical certificate dated 10/24/00, with a limitation to wear corrective lenses. The last flight logged in the pilot's flight logbook, prior to the accident flight, was on April 26, 2001, in the R44.

Aircraft information

The helicopter was manufactured by Robinson Helicopter, Torrance, California, and signed off as meeting the requirements for the certification requested and issued a Standard Airworthiness Certificate dated January 12, 2001, at a total flight time of five hours, and serial number 0972. The helicopter was picked up on January 13, 2001, by the registered owner and accompanied by the flight instructor who was involved in the accident. The helicopter was flown to Boeing Field, arriving on January 15, 2001. The helicopter was maintained and operated by Classic Helicopter for the purposes of rental and instructional flights.

Maintenance records indicated that the helicopter was being maintained in accordance with a 100 hour inspection program. The one and only 100 hour inspection was accomplished on April 4, 2001, at a total flight time of 103.9 hours. The helicopter accumulated a total flight time of approximately 131 hours at the time of the accident.

Communications

Air Traffic Control communications obtained from Boeing Field tower indicated that at 0906, the pilot requested departure from pad 1 for a "west steam plant departure." The tower controller approved the departure as requested. There were no other recorded communications from the flight prior to the accident.

Personnel at Classic Helicopter reported that the steam plant departure is for helicopters departing from pad 1 in front of the Classic Helicopter facility. The helicopter fly’s below 100 feet until after crossing the extended runway center line, then climb as necessary.

Wreckage and impact information

NTSB personnel arrived at the accident site on May 11, 2001, about 1230. The wreckage was located in an area that was heavily wooded with trees varying in height up to about 100 feet. The relatively level ground was covered with thick underbrush. Accident site coordinates were obtained via a hand held GPS at N47 degrees 28.639' W122 degrees 42.087', and an elevation of approximately 440 feet mean sea level. The surrounding area was sparsely populated with residential housing. South of the accident site about 1/4 to 1/2 miles is the Trophy Lakes Golf Course. A resident with an open horse pasture was to the south, and one of the two Nels Johnson Lakes was about 200 feet north of the main wreckage.

The main wreckage consisting of the fuselage and inboard section of the tail boom, minus the empennage section, were located at the base of an approximate 100 foot tree. About 30 feet up from the base of the tree, an approximate 60 degree deep slash mark (as measured from horizontal) was located, with additional damage to the trunk about 15 feet below. A post-crash fire consumed the cockpit area. The fuselage was positioned with its nose oriented about 320 degrees magnetic. The fuselage was laying on its left side. A 10.5 foot section of the tail boom remained in its respective position to the airframe. The tail rotor drive shaft was pulled partially out of the boom structure. One main rotor blade remained attached to the hub. The blade was severely bowed and displayed heat distress. The other main rotor blade separated. About 20 inches of the blade remained attached to the hub. The engine remained in place and displayed severe heat distress.

A search of the surrounding area located several pieces of the main rotor blades up to and in excess of about 180 feet to the south of the main wreckage. Both tail rotor blades had separated from the tail rotor hub. Damage was consistent with the pitch change link being in place at impact. One blade was found in close proximity to the main wreckage. The other blade had been removed by one of the witnesses, and then later retrieved by NTSB personnel. The witness reported its approximate location which was about 80 feet south of the main wreckage.

The empennage section with the upper and lower vertical stabilizer and the horizontal stabilizer attached was located about 180 feet south of the main wreckage. A 22 inch section of the aft tail boom with the tail rotor drive shaft contained within the structure remained attached. The separated end of the drive shaft was severely twisted. The skin at the separation point was severely deformed and appeared torn. The tail rotor gear box driving gear remained, however, the tail rotor assembly had separated. No leading edge damage was noted to the stabilizers. Slight wrinkling to the skin on the right side of the upper vertical stabilizer